[FFmpeg-trac] #9160(ffmpeg:new): ffmpeg stuck at initialization

[FFmpeg]

#9160: ffmpeg stuck at initialization
--------------------------------+--------------------------------------
             Reporter:  Gyan    |                     Type:  defect
               Status:  new     |                 Priority:  important
            Component:  ffmpeg  |                  Version:  git-master
             Keywords:          |               Blocked By:
             Blocking:          |  Reproduced by developer:  0
Analyzed by developer:  0       |
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 ffmpeg gets stuck at initialization with the following command, with a CPU
 core running steady near 100%:

 {{{
 cat video.ts | ffmpeg -i - -f image2 -loop 1 -re -i image.png
 -filter_complex
 "[0:v]scale=iw:ih[in];[1][in]scale2ref[img][in1];[in1][img]overlay[out]"
 -map "[out]" -map 0:a -f null -
 }}}

 The sufficient and necessary conditions appear to be that the first input
 be non-seekable, and the image input have the `-re` flag applied. Removing
 either of these conditions and the issue disappears.

 Based on the nature I suspected that one or more commits made to ffmpeg.c
 in Oct 2020 might be the culprit. And indeed, the issue doesn't occur with
 my 2020-10-28 build but does occur with my 2020-10-31 build. The commits I
 suspect are 67be1ce0c6 and 7369595c55.

 How to generate inputs:

 {{{
 ffmpeg -f lavfi -i testsrc2 -f lavfi -i sine -t 5 video.ts

 ffmpeg -f lavfi -i mandelbrot -vframes 1 image.png
 }}}

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Ticket URL: <https://trac.ffmpeg.org/ticket/9160>
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